A multipolar single-head plug and a corresponding multipolar jack have conventionally been used for electrical connection of various electronic devices. As an example, a connector is composed of a multipolar single-head plug provided to a peripheral electronic device such as a headphone and a multipolar jack provided to the body of an electronic device such as a multifunctional portable phone or a portable music player.
This multipolar single-head plug has a core bar to be inserted in the multipolar jack. The core bar is given a bar electrode exposed at a tip and one or multiple tubular electrodes exposed at an outer circumference on a side closer to a root than the bar electrode. An insulating part intervenes between the bar electrode and the tubular electrode. If there are multiple tubular electrodes, the insulating part intervenes between these tubular electrodes. As a result, properties of insulation between the electrodes are maintained. The multipolar single-head plug is generally formed to be in conformity with or compatible with standards relating to single-head plugs and jacks defined in Japanese Industrial Standards or standards of Japan Electronics and Information Technology Industries Association (see patent literature 1).